US20070115773A1 - Method for adaptively driving a tracking element with mechanical deviation and device using the same - Google Patents
Method for adaptively driving a tracking element with mechanical deviation and device using the same Download PDFInfo
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- US20070115773A1 US20070115773A1 US11/460,719 US46071906A US2007115773A1 US 20070115773 A1 US20070115773 A1 US 20070115773A1 US 46071906 A US46071906 A US 46071906A US 2007115773 A1 US2007115773 A1 US 2007115773A1
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- motor
- standard
- moving time
- driving
- tracking element
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
- G11B7/0857—Arrangements for mechanically moving the whole head
- G11B7/08582—Sled-type positioners
Abstract
Description
- This application claims the priority benefit of Taiwan application serial no. 94140561, filed on Nov. 18, 2005. All disclosure of the Taiwan application is incorporated herein by reference.
- 1. Field of the Invention
- The present invention relates to a method for driving a tracking element and a driving device using the same. More particularly, the present invention relates to a method for adaptively driving a tracking element with mechanical deviation and a driving device using the same.
- 2. Description of Related Art
-
FIG. 1A is a view of a driving mechanism of a conventional optical disc drive. The mechanism of the optical disc drive includes atransmission bar 101, anoptical head 102, amirror mount 103, atracking gear set 104, and asledge tracking motor 105. Thesledge tracking motor 105 pushes theoptical head 102 to move along thetransmission bars 101 through thetracking gear set 104. Themirror mount 103 is disposed on theoptical head 102 for focusing the light beams emitted from inside theoptical head 102 to access data.FIG. 1B is a motion graph of the driving mechanism of a conventional optical disc drive. In general, as theoptical disc 107 has a large number of tracks, dual stoppers are usually used to reduce the moving time of theoptical head 102 to the position to be read. First, theoptical head 102 is forced to move a longer distance, for example, across hundreds of tracks, by thesledge tracking motor 105. Next, themirror mount 103 is forced to move a shorter distance, for example, less than a track, by thestopper 106 inside the optical head, so as to reduce the reading time and improve the precision by division of work. - Referring to
FIGS. 1A and 1B , in order to move themirror mount 103 to the position SD to read the data in theoptical disc 107, generally theoptical head 102 is forced to move from the position SA to SB by thesledge tracking motor 105. Next, themirror mount 103 is forced to move from the position SC to SD by thestopper 106 inside the optical head. In general, the principle of the motion mechanism of the optical disc drive is to supply the voltage to thesledge tracking motor 105. When thesledge tracking motor 105 is initiated, thetracking gear set 104 is driven to bring theoptical head 102 gliding on thetransmission bars 101. Therefore, theoptical head 102 is forced to move a long distance, for example, across hundreds of tracks. Next, thestopper 106 inside the optical head (usually a voice coil motor) pushes themirror mount 103 moving a short distance according to the principle of electromagnetic induction, so as to track more precisely. - When the
optical head 102 is moving, in order to make theoptical head 102 reach the predetermined position, track crossing signals on theoptical disc 107 are detected (i.e., using the radio frequency (RF) and the tracking error (TE) signals for mutual determination) for correcting the position and speed. However, when the friction changes, for example, the friction increases due to the bad engagement of the gear set, the open loop cannot compensate completely. Therefore, the optical disc drive adopting such a gear set is regarded as unqualified. - An object of the invention is to provide a method for adaptively driving a tracking element with mechanical deviation. The method can overcome poor performance of the tracking servo due to variance factors such as the assembly difference of the tracking element (for example, the difference of the assembly position between the transmission gear and the sledge motor gear during the assembly), aging of the tracking element (for example, the deformation of the gear after a long-term usage), the manufacturing difference of the element (for example, the specification difference of the shape of the gear), expansion due to heat and contraction due to cold or change of in the viscosity coefficient of the lubricant oil due to environmental changes (for example, different temperature and humidity).
- Another object of the invention is to provide a driving device for adaptively driving a tracking element with mechanical deviation. This device can overcome poor performance of the tracking servo due to the variance factors such as the assembly difference of the tracking element, aging variance of the tracking element, the manufacturing difference of the element, the environmental change factors.
- In accordance with the above and other objects of the present invention, a method for adaptively driving a tracking element with mechanical deviation is provided. In the method, a tracking element is driven by a motor, and the method for driving the tracking element includes the following steps. First, the standard moving time of a standard tracking element and the standard motor current value are recorded. A driving voltage is supplied to a motor for driving a tracking element. The current value of the motor and the moving time of the tracking element are detected. And then, a driving gain of the motor based on the relation between the current value of the motor and the standard motor current value are adjusted based on the relation between the moving time of the tracking element and the standard moving time of the standard one.
- The method for adaptively driving a tracking element with mechanical deviation according to the preferred embodiment of the invention further includes supplying a standard driving voltage to a standard motor for driving a standard tracking element to track back and froth once; detecting the current value of the standard motor as the standard motor current value; and detecting the moving time of the standard tracking element as the standard moving time. The step of recording the standard moving time and the standard motor current value includes recording the standard moving time and the standard motor current value into a non-volatile memory. And the step of adjusting a driving gain of the motor includes raising the driving voltage when the current value of the motor is larger than the standard current value; supplying the raised driving voltage to the motor for driving a tracking element to track back and froth once; detecting the moving time of the tracking element; and comparing the moving time of the tracking element and the standard moving time to ascertain whether they are equal. However, when the moving time of the tracking element approaches the standard moving time, the proportion of increasing the driving gain of the motor is determined by the proportion of the raised driving voltage and the standard driving voltage.
- According to an aspect of the present invention, the step of adjusting a driving gain of the motor includes reducing the driving voltage when the current value of the motor is lower than the standard current value; supplying the reduced driving voltage to the motor for driving the tracking element to track back and froth once; detecting the moving time of the tracking element, and comparing the moving time of the tracking element and the standard moving time to ascertain whether they are equal. When the moving time of the tracking element approaches the standard moving time, the proportion of reducing the driving gain of the motor is determined by the proportion between the reduced driving voltage and the standard driving voltage. The method for adaptively driving a tracking element with mechanical deviation can be applied to the tracking mechanism of an optical disc drive, and the tracking element includes a sledge tracking element.
- According to another aspect of the present invention, a device for adaptively driving a tracking element with mechanical deviation is adopted for controlling a motor to drive a tracing element. The driving device of the tracking element includes a memory, a motor driver, a current detecting circuit and a processor. The memory is used to record the standard moving time and the standard current value. The motor driver, electrically connected to the motor is used to output the driving voltage to the motor in accordance with the control signal for driving the tracking element. The current detecting circuit is electrically connected to the motor for detecting the current of the motor to be adjusted. The processor is electrically connected to the memory, the motor driver and the current detecting circuit for outputting control signal to control the motor driver and measuring the moving time of the tracking element. The processor controls the motor driver to adjust the driving gain of the motor based on the relation between the current value of the motor measured by the current detecting circuit and the standard motor current value recorded in the memory, and based on the relation between the moving time of the tracking element and the standard moving time.
- According to an aspect of the present invention, the standard driving voltage is supplied to a standard motor for driving the standard tracking element to track back and froth once for detecting the current value of the standard motor as the standard motor current value, and then the moving time of the standard tracking element as the standard moving time is detected. The memory can be a non-volatile memory. When the current value of the motor is higher than the standard current value, the processor controls the motor driver to raise the driving voltage and supplies the raised driving voltage to the motor for driving the tracking element to track back and froth once to detect the moving time of the tracking element.
- According to an aspect of the present invention, when the processor compares and determines that the moving time value of the tracking element is not the same as the standard moving time value, the driving voltage is raised again and the moving time of the tracking element is compared with the standard moving time, wherein when the moving time value of the tracking element approaches the standard moving time value, the proportion of increasing the driving gain of the motor is determined by the proportion between the increased driving voltage and the standard driving voltage. When the current value of the motor is smaller than the standard current value, the processor controls the motor driver to reduce the driving voltage, and supplies the reduced driving voltage to the motor for driving the tracking element to track back and froth once, so as to detect the moving time of the tracking element. Then, when the processor compares and detects that the moving time value of the tracking element is not the same as the standard moving time value, the driving voltage is reduced again and the moving time of the tracking element is compared with the standard moving time. And, when the moving time value of the tracking element approaches the standard moving time value, the proportion of reducing the driving gain of the motor is determined by the proportion between the decreased driving voltage and the standard driving voltage. The device for adaptively driving a tracking element with mechanical deviation can be applied to the tracking mechanism of an optical disc drive. The tracking element includes a sledge tracking element.
- As the controller gain of the motor is adjusted according to the load current value of the standard motor by detecting the changes of the load current of the motor, the variance factors affecting the performance of the tracking servo, such as the assembly position difference due to the assembly of the tracking element, the deformation caused due to the aging of the tracking element, the specification difference of the manufactured form of the element, expansion due to heat and contraction due to cold or the change of the viscosity coefficient of the lubricant oil caused by the environmental factors may be effectively reduced.
- In order to the make the aforementioned and other objects, features and advantages of the present invention comprehensible, a preferred embodiment accompanied with figures is described in detail below.
-
FIG. 1A is a reference diagram of a driving mechanism of a conventional optical disc drive. -
FIG. 1B is a graph showing the motion of the driving mechanism of a conventional optical disc drive. -
FIG. 2 is a circuit diagram illustrating the trackingDC motor 200. -
FIG. 3 is a flow chart illustrating the recording of the standard moving time and the current value of the standard DC motor according to the embodiment of the invention. -
FIG. 4 is a timing diagram of detecting the load degree of the tracking DC motor. -
FIG. 5 is a flow chart of the method for adaptively driving a tracking element with mechanical deviation according to the embodiment of the invention. -
FIG. 6 is a circuit block view of the device for adaptively driving a tracking element with mechanical deviation and a sledge tracking DC motor. -
FIG. 2 is an equivalent circuit diagram illustrating atracking DC motor 200. The circuit of the DC motor can be represented by the following expression:
where, Va represents the voltage at both ends of theDC motor 200; Ra represents the armature resistance; La represents armature inductance; ia represents the current value passing through Ra; t represents time; and
represents a differential of the current value ia to the time t. The expression indicates the voltage distribution inside the trackingDC motor 200. Then, assuming the armature inductance La of the trackingDC motor 200 is 0, the expression (1) is simplified to be the following expression:
Va =Ra·ia +Ea (2)
The back electromotive force Ea of the trackingDC motor 200 can be represented by the following expression:
Ea =Kb·ω (3)
where, Kb represents back electromotive force coefficient, and ω represents the rotational angular speed of the motor. The angular speed ω affects the back electromotive force Ea. - When a constant voltage Va is supplied to the tracking
DC motor 200, the trackingDC motor 200 has a constant rotational angular speed ω under the constant friction. Referring to expressions (2) and (3) at the same time, under the constant voltage Va, if the rotational angular speed ω of the trackingDC motor 200 is reduced due to the over friction, the back electromotive force Ea is reduced accordingly. However, under the condition of constant voltage Va, the current value ia is increased. On the other hand, if the angular speed ω of the trackingDC motor 200 is increased due to the reduced friction, the back electromotive force Ea is increased, and under the constant voltage Va, the current value ia is reduced. Therefore, the changes of the friction can be obtained by detecting the changes of the current value ia. -
FIG. 3 is a flow chart illustrating the recording of the standard moving time and the current value of the standard tracking DC motor according to the embodiment of the invention. First, in Step S301, the standard mechanism is sampled and the tracking motor starts to detect. The standard mechanism comprises, for example, a standard motor and a standard tracking element (elements such as a transmission shaft, tracking gear required for moving the optical head) of an optical disc drive. As the standard transmission shaft and the standard tracking gear set are sophisticated and well assembled, a desired tracking time is achieved in reaching the desired track. Next, in Step S303, the standard driving voltage VS is supplied to a standard motor for driving a standard tracking element to track back and froth once, and detecting the average current value of the standard motor as the standard current value iS and the moving time as the standard moving time TS. In Step S303, the design of the tracking element moving back and froth once is that the tracking system moves in the same mechanism model, so the moving distance is fixed. The moving time of the tracking element is detected under the circumstance that the tracking element moves a fixed distance, thereby deducing the condition of the moving speed of the tracking element under the influence of friction. Next, in Step S305, the standard current value iS and the standard moving time TS are recorded and stored in a memory, such as a non-volatile memory. The stored standard current value iS and the standard moving time TS can be taken as a reference when adjusting the voltage gain of other tracking DC motors during mass production, thereby achieving a better tracking performance of various motors. Meanwhile, when the tracking element ages, the standard current value and the standard moving time can also be used as the standard for adjusting the tracking motor of the aging tracking element. The viscosity coefficient of the lubricant oil of the tracking element is influenced by the temperature and humidity in different environmental conditions (for example, the area in the latitude far from the producing area), so that the standard data can also be the reference for adjusting. -
FIG. 4 is a timing diagram of detecting the load degree of the tracking DC motor. Referring to the aforementioned expressions (2), (3) andFIG. 4 , the scheme of detecting the current value of the motor and the moving time of the tracking element is illustrated.FIG. 4 indicates the corresponding relation of the voltage Va of the tracking DC motor, the current value ia of the tracking DC motor and the clock signal. During thetime period 0˜TA, as the tracking element has not moved, the angular speed of the motor is 0 and the current value remains the maximum i1. During the time period TA˜TB, as the tracking element starts to move, the rotational angular speed of the motor is increased and the back electromotive force of the motor is increased. While under the constant voltage V1, the current value at this time is reduced to i2. During the time period TB˜TC, the tracking element has moved to the outermost track and will stop due to the limitation of the length of the track mechanism, and then the tracking element is at a fixed position. Therefore, the rotational angular speed of the tracking element returns to 0 as the tracking element stops moving, and the current value returns to its maximum i1. As a result, the moving time of the tracking element is represented as TA ˜TB, and the current value when the motor pushes the tracking element is represented as i2. -
FIG. 5 is a flow chart of a method for adaptively driving a tracking element with mechanical deviation according to the embodiment of the invention. First, in Step S501, the standard moving time TS and the standard current value iS are recorded, by referring to Steps S301˜S305 of recording the standard moving time and the standard motor current value of the standard tracking DC motor inFIG. 3 . In Step S502, the current value of the tracking motor of the mechanism from mass production is recorded. In Step S503, the driving voltage Va (the initial value is, for example, the standard voltage VS ) is supplied to the motor for driving the tracking element to track in and out once, and then detecting the average current value iA of the motor and the moving time T. Thus, in Step S505, the average current value iA of the motor from mass production and the average current value iS of the standard motor are compared to see whether they are equal. If the average current value iA of the motor is equal to the average current value iS of the standard motor, the procedure proceeds to Step S507, indicating that the adjusting operation is completed without correcting the gain of the motor in the tracking system. If the average current value iA of the motor and the average current value iS of the standard motor are not same, then the procedure proceeds to Step S509 for further determination. - In Step S509, the average current value iA of the motor and the average current value iS of the standard motor are compared. When the average current value iA of the motor is larger than the average current value iS of the standard motor, the angular speed of the motor is reduced due to the increase of the friction, and then proceed to Step S511, i.e., raising the driving voltage Va of the motor for driving the tracking element to track in and out once again and detecting the average current value iA of the motor and the moving time T. Thereafter, in Step S513, the moving time T and the standard moving time TS are compared to see whether they are equal. When the moving time T are not the same as the standard moving time TS, the procedure returns to Step S511 to increase the voltage Va again until the moving time T is equal the standard moving time TS. When the moving time T is equal to the standard moving time TS, the driving voltage Va of the motor is the final voltage Va_f. In Step S515, the proportion of raising the voltage of the tracking motor (Va_f/VS) can be obtained based on the final voltage Va_f and the standard voltage VS. The proportion of increasing the driving gain of the motor is determined by the proportion of raising the voltage, i.e., the driving voltage levels supplied to the tracking motor during the normal operation are all amplified in the same proportion. When the friction of the gears of the tracking element is increased due to the small gear backlash during the manufacture, the voltage can also be adjusted by the driving method, thus the tracking element with mechanical deviation functions properly.
- In the above Step S509, if the comparison result is the average current value iA of the motor smaller than the average current value iS of the standard motor, the procedure proceeds to Step S517. In Step S517, the driving voltage Va of the motor is reduced for driving the tracking element to track in and out once again, and detects the average current value iA of the motor and the moving time T. Next, in Step S519, the moving time T and the standard moving time TS are compared to ascertain whether they are equal. When the moving time T and the standard moving time TS are not equal, the procedure returns to Step S517 to reduce the voltage Va until the moving time T is equal to the standard moving time TS. When the moving time T is equal to the standard moving time TS, the driving voltage Va is the final voltage Va_f. In Step S521, the proportion of reducing the voltage of the tracking motor (Va_f/VS) can be obtained based on relation between the final voltage Va_f and the standard voltage VS. Also, the proportion of reducing the driving gain of the motor is determined by the proportion of reducing the voltage, i.e., the driving voltage levels supplied to the tracking motor during the normal operation are all reduced in the same proportion.
- The driving method according to the above embodiment can be used for driving the tracking mechanism of an optical disc drive, such as a sledge tracking element. Besides, in the aforementioned embodiment, the above adjustment mechanism can be initiated as desired. Therefore, the method for driving a tracking element can overcome the assembly position variance occurring during the assembly of the tracking element (for example, the over-sized gear backlash of the tracking gear set of the tracking element), thereby remarkably increasing the product yield. Moreover, the method for driving a tracking element according to the above embodiment can also overcome the influences caused by variance factors such as the deformation due to the aging of the tracking element, the specification difference of the manufactured form of the element, expansion due to heat and contraction due to cold or the change of the viscosity coefficient of the lubricant oil caused by the environmental conditions, thereby adaptively and promptly adjust the driving gain of the motor.
-
FIG. 6 is a circuit block view of the device for adaptively driving a tracking element with mechanism difference and a sledge tracking DC motor according to the embodiment of the invention. By reference, thedevice 61 for adaptively driving a tracking element with mechanical deviation controls thesledge DC motor 62 to drive the tracking element (not shown). The drivingdevice 61 includes amemory 601, amotor driver 602, a current detectingcircuit 603, and aprocessor 604. Thememory 601 is used to record the standard moving time and the standard current value. Themotor driver 602 is electrically connected to the sledge trackingDC motor 62 for outputting the corresponding driving voltage according to the control signal and supplying the driving voltage to the sledge trackingDC motor 62 to drive the tracking element. The current detectingcircuit 603 is electrically connected to the sledge trackingDC motor 62 for detecting the current value of the trackingDC motor 62. Theprocessor 604 is electrically connected to thememory 601, themotor driver 602, the current detectingcircuit 603, for controlling themotor driver 602 by outputting control signals, and measuring the moving time of the tracking element. Theprocessor 604 controls themotor driver 602 to adjust the driving gain of the sledge trackingDC motor 62 based on the relation between the current value of the sledge trackingDC motor 62 detected by the current detectingcircuit 603 and the standard current value recorded in thememory 601, and based on the relation between the moving time of the tracking element and the standard moving time recorded in thememory 601. - The
memory 601 of the drivingdevice 61 can be a non-volatile memory. The standard moving time and the standard current value stored in thememory 601 are resulted from supplying the standard driving voltage to the standard motor for driving the standard tracking element to track back and froth once and detecting the current value of the standard motor as the standard motor current value, and detecting the moving time of the standard tracking element as the standard moving time. - After detection by the current detecting
circuit 603, when the current value of the sledge trackingDC motor 62 is larger than the standard motor current value, theprocessor 604 controls themotor driver 602 to raise the driving voltage, and supplies the raised driving voltage to the sledge trackingDC motor 62 for driving the tracking element to track back and froth once, thereby detect the moving time of the tracking element. Then, when theprocessor 604 compares and determines that the moving time of the tracking element is not equal to the standard moving time, the driving voltage is raised again and the moving time of the tracking element is compared with the standard moving time until the moving time is equal to the standard moving time. When the moving time of the tracking element is equal to the standard moving time, the proportion of increasing the driving gain of the motor is determined by the proportion between the raised driving voltage and the standard driving voltage. - After detection by the current detecting
circuit 603, when the current value of the sledge trackingDC motor 62 is smaller than the standard motor current value, theprocessor 604 controls themotor driver 602 to reduce the driving voltage, and supplies the reduced driving voltage to the sledge trackingDC motor 62 for driving the tracking element to track back and froth once, thereby detect the moving time of the tracking element. Then, when theprocessor 604 compares and determines that the moving time of the tracking element is not equal to the standard moving time , the driving voltage is reduced again and the moving time of the tracking element is compared with the standard moving time until the moving time is equal to the standard moving time. When the moving time of the tracking element is equal to the standard moving time, the proportion of reducing the driving gain of the motor is determined by the proportion between the reduced driving voltage and the standard driving voltage. - The tracking element can be a sledge tracking element. The device for adaptively driving a tracking element with mechanical deviation can be applied to drive the tracking system of an optical disc drive. However, those skilled in the art should understand the application of the invention is not limited to this and any servo parameters using the changes of the current passing through the tracking DC motor to deduce the friction between the gears and adjust the tracking system fall within the scope of the invention.
- In view of the above, the method for adaptively driving a tracking element with mechanical deviation and device using the same is adopted for comparing the moving time of the standard tracking element with the moving time of the tracking element to be adjusted and comparing the current value of the motor to continuously adjust the voltage gain of the motor by supplying different voltages according to different detection results. Therefore, the problems influencing the performance of the tracking element such as the assembly difference, manufacturing difference, differential environmental conditions, and element aging can be overcome. Thus, the product yield, the tracking quality and service life of the tracking element can be effectively increased.
- Though the present invention has been disclosed above by the preferred embodiments, it is not intended to limit the invention. Anybody skilled in the art can make some modifications and variations without departing from the spirit and scope of the invention. Therefore, the protecting range of the invention falls in the appended claims.
Claims (16)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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TW94140561A | 2005-11-18 | ||
TW094140561A TWI306688B (en) | 2005-11-18 | 2005-11-18 | Method for adaptively driving a tracking element with mechanical deviation and device using the same |
TW94140561 | 2005-11-18 |
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US20070115773A1 true US20070115773A1 (en) | 2007-05-24 |
US8050153B2 US8050153B2 (en) | 2011-11-01 |
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US11/460,719 Expired - Fee Related US8050153B2 (en) | 2005-11-18 | 2006-07-28 | Method for adaptively driving a tracking element with mechanical deviation and device using the same |
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TW (1) | TWI306688B (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20050068856A1 (en) * | 2003-09-29 | 2005-03-31 | Lite-On It Corporation | Method of on-line adjusting a sled motor control signal (FMO) |
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US6266046B1 (en) * | 1996-05-29 | 2001-07-24 | Fujitsu Takamisawa Component Ltd. | Pointing device for moving and positioning a pointer on a display of a computer |
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- 2005-11-18 TW TW094140561A patent/TWI306688B/en active
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US5432530A (en) * | 1991-05-15 | 1995-07-11 | Fujitsu Limited | Pointing device and method of control of same |
US5714980A (en) * | 1995-10-31 | 1998-02-03 | Mitsumi Electric Co., Ltd. | Pointing device |
US5859742A (en) * | 1995-11-17 | 1999-01-12 | Fujitsu Limited | Disk storage apparatus having head overshoot and undershoot control |
US6266046B1 (en) * | 1996-05-29 | 2001-07-24 | Fujitsu Takamisawa Component Ltd. | Pointing device for moving and positioning a pointer on a display of a computer |
US6226242B1 (en) * | 1998-01-09 | 2001-05-01 | Sanyo Electric Co., Ltd. | Disk recording of playback device and method of controlling pickup of the device |
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US6583784B1 (en) * | 1999-12-29 | 2003-06-24 | Honeywell International Inc. | Pointing device based upon the hall effect and method for operating the same |
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Publication number | Priority date | Publication date | Assignee | Title |
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US20050068856A1 (en) * | 2003-09-29 | 2005-03-31 | Lite-On It Corporation | Method of on-line adjusting a sled motor control signal (FMO) |
Also Published As
Publication number | Publication date |
---|---|
US8050153B2 (en) | 2011-11-01 |
TWI306688B (en) | 2009-02-21 |
TW200721659A (en) | 2007-06-01 |
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